Semiconductor device

ABSTRACT

A semiconductor device includes a semiconductor substrate 10 of a first conductivity type, a vertical Hall element 100 provided on the semiconductor substrate 10, and an excitation conductor 200 provided directly above the vertical Hall element 100 with an intermediation of an insulating film 30. The vertical Hall element 100 includes a semiconductor layer 101 of a second conductivity type provided on the semiconductor substrate 10, and a plurality of electrodes 111 through 115 each constituted from a high-concentration second conductivity type impurity region and provided on the surface of the semiconductor layer 101 along a straight line. A ratio W C /W H  between a width W C  of the excitation conductor 200 and a width W H  of each of the plurality of electrodes 111 through 115 satisfies 0.3≤W C /W H ≤1.0.

RELATED APPLICATIONS

Priority is claimed on Japanese Patent Application No. 2018-126683,filed on Jul. 3, 2018, the content of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a semiconductor device, andparticularly to a semiconductor device including a vertical Hall elementwhich detects a horizontal magnetic field.

2. Description of the Related Art

A Hall element has been used for various applications because ofpossible non-contact detection of position and angle as a magneticsensor. Of these, a magnetic sensor using a horizontal Hall elementdetecting a magnetic field component perpendicular to the surface of thesemiconductor substrate has generally been known well, and variousmagnetic sensors each using a vertical Hall element detecting a magneticfield component parallel to the surface of the semiconductor substratehave also been proposed. Further, there has also been proposed amagnetic sensor which makes two-dimensional or three-dimensionaldetection of a magnetic field by combining a horizontal Hall element anda vertical Hall element.

Characteristics variation of a vertical Hall element is, however, largesince sensitivity and offset voltage characteristics of the verticalHall element is apt to be affected by production variation as comparedwith the horizontal Hall element.

In order to calibrate such characteristics variation, there has beendisclosed in U.S. Pat. No. 9,116,192, a method for estimation of thesensitivity of the Hall element in which a current flows through anexcitation conductor disposed in the vicinity of a vertical Hall elementto thereby generate a calibration magnetic field having a predeterminedmagnetic flux density in the position of the Hall element. That is, theactual sensitivity of the Hall element is estimated by changing themagnetic flux density of the calibration magnetic field and measuring achange in a Hall voltage supplied from the Hall element during theapplication of the calibration magnetic field.

Further, there has been illustrated in FIG. 1 of U.S. Pat. No.9,116,192, a structure in which the horizontal distance between thecenter of an excitation conductor and the center of a vertical Hallelement is separated, i.e., the center of the excitation conductor isshifted in a horizontal direction from the center of the vertical Hallelement. It is thus possible to suppress the vertical Hall element frombeing affected by variation in a magnetic field intensity generated bythe excitation conductor due to variation in the width of the excitationconductor, etc., by a process fluctuation during the manufacture of asemiconductor device.

The structure illustrated in FIG. 1 of U.S. Pat. No. 9,116,192 howeverinvolves the following drawbacks.

That is, the distance between the vertical Hall element and theexcitation conductor is enlarged by separating the horizontal distancebetween the center of the excitation conductor and the center of thevertical Hall element. Since the magnetic field intensity generated bythe current flowing through the excitation conductor is inverselyproportional to the distance from the excitation conductor, theintensity of the calibration magnetic field applied to the vertical Hallelement becomes small when the distance between the vertical Hallelement and the excitation conductor becomes large.

A change in the Hall voltage supplied from the vertical Hall elementbecomes small when the intensity of the calibration magnetic fieldapplied to the vertical Hall element becomes small. It is thus possibleto suppress variation in the intensity of the calibration magnetic fieldapplied to the vertical Hall element, but since the intensity of thecalibration magnetic field reduces, accuracy in estimating actualsensitivity of the vertical Hall element degrades as a result.

The current flowing through the excitation conductor is accordinglyincreased to enlarge the intensity of the calibration magnetic fieldapplied to the vertical Hall element: the amount of heat generation fromthe excitation conductor thereby increases. In U.S. Pat. No. 9,116,192,the center of the excitation conductor is shifted in the horizontaldirection from the center of the vertical Hall element, whereby theexcitation conductor approaches to a peripheral circuit such as acircuit which processes an output signal from the vertical Hall element,a circuit to supply a signal to the vertical Hall element, or the like,and which are disposed around the vertical Hall element. Temperaturedistribution therefore occurs in the peripheral circuit due to the heatgeneration of the excitation conductor. The characteristics of theperipheral circuit thereby fluctuate, thus leading to degradation of theaccuracy in estimating actual characteristics of the vertical Hallelement.

Incidentally, increasing the distance between the excitation conductorand the peripheral circuit may suppress the generation of thetemperature distribution in the peripheral circuit, but may not berealistic because of heading against the miniaturization of thesemiconductor device.

SUMMARY OF THE INVENTION

The present invention therefore aims to provide a semiconductor devicecapable of suppressing heating of an excitation conductor from affectinga peripheral circuit, enlarging the intensity of a calibration magneticfield received by a vertical Hall element, and thereby performinghigh-accuracy calibration of the vertical Hall element.

A semiconductor device according to one aspect of the present inventionis provided which includes a semiconductor substrate of a firstconductivity type, a vertical Hall element provided on the semiconductorsubstrate, and an excitation conductor provided directly above thevertical Hall element with an intermediation of an insulating film. Thevertical Hall element includes a semiconductor layer of a secondconductivity type provided on the semiconductor substrate, and aplurality of electrodes each constituted from a high-concentrationsecond conductivity type impurity region and provided on the surface ofthe semiconductor layer along a straight line. A ratio W_(C)/W_(H)between a width W_(C) of the excitation conductor and a width W_(H) ofeach of the plurality of electrodes satisfying an inequality0.3≤W_(C)/W_(H)≤1.0.

According to the present invention, the excitation conductor is disposeddirectly above the vertical Hall element, and the ratio W_(C)/W_(H)between the width W_(C) of the excitation conductor and the width W_(H)of each electrode of the vertical Hall element is assumed to be lessthan or equal to 1.0, whereby a peripheral circuit such as a circuitprocessing an output signal from the vertical Hall element, a circuit tosupply a signal to the vertical Hall element, or the like, and theexcitation conductor can be disposed so as not to approach each other.Also, since it is possible to suppress an increase in the amount of heatgeneration from the excitation conductor by setting W_(C)/W_(H) to begreater than or equal to 0.3, occurrence of a temperature distributionin the peripheral circuit can be prevented. Further, the intensity of acalibration magnetic field received by the vertical Hall element can beenlarged by disposing the excitation conductor directly above thevertical Hall element. It is thus possible to enlarge the intensity ofthe calibration magnetic field applied to the vertical Hall element andperform calibration of the vertical Hall element with high accuracywhile suppressing the amount of heat generation from the excitationconductor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view of a semiconductor device having a vertical Hallelement according to an embodiment of the present invention, and FIG. 1Bis a sectional view taken along line L-L′ of FIG. 1A;

FIG. 2 is a graph illustrating a result in which a relation between aratio (W_(C)/W_(H)) between a width W_(C) of an excitation conductor anda width W_(H) of each electrode of the vertical Hall element and anincrease in the temperature of the excitation conductor when theexcitation conductor generates a magnetic field having a magnetic fluxdensity of 2 mT is simulated by changing a ratio (h/W_(H)) between adistance h from the center of the vertical Hall element in a substratedepthwise direction to the excitation conductor and the width W_(H) ofeach electrode of the vertical Hall element; and

FIG. 3 is a graph illustrating a result in which a relation between theratio (W_(C)/W_(H)) between the width W_(C) of the excitation conductorand the width W_(H) of each electrode of the vertical Hall element and amagnetic flux density (B/I) applied to the vertical Hall element perunit current flowing through the excitation conductor is simulated bychanging the ratio (h/W_(H)) between the distance h from the center ofthe vertical Hall element in a substrate depthwise direction to theexcitation conductor 200 and the width W_(H) of each electrode of thevertical Hall element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will hereinafter be described indetail with reference to the accompanying drawings.

FIG. 1 is a view for describing a semiconductor device having a verticalHall element according to the embodiment of the present invention inwhich FIG. 1A is a plan view, and FIG. 1B is a sectional view takenalong line L-L′ of FIG. 1A.

As illustrated in FIG. 1, the semiconductor device according to thepresent embodiment includes a semiconductor substrate 10 of a P type(first conductivity type), a P-type element isolation diffusion layer20, a vertical Hall element 100 provided on the semiconductor substrate10, an insulating film 30 provided on the vertical Hall element 100, andan excitation conductor 200 provided on the insulating film 30.

The vertical Hall element 100 is constituted from an N type (secondconductivity type) semiconductor layer 101 serving as a magnetismsensing part which is provided on the semiconductor substrate 10, andelectrodes 111 through 115 each constituted from an N type impurityregion are provided on the surface of the semiconductor layer 101 alonga straight line. The electrodes 111 through 115 have a rectangular shapeand a common width W_(H) and are provided in parallel to each other.

The element isolation diffusion layer 20 electrically isolates thevertical Hall element 100 from other regions (not illustrated) on thesemiconductor substrate 10.

Elements such as transistors provided in other regions on thesemiconductor substrate 10 electrically isolated from the vertical Hallelement 100 by the element isolation diffusion layer 20. The elementsconstitute a circuit which processes an output signal from the verticalHall element 100, a circuit which supplies a signal to the vertical Hallelement 100, or a circuit which compensates the characteristics of thevertical Hall element 100 by a calibration magnetic field, or the like(hereinafter called a “peripheral circuit”).

The excitation conductor 200 has a linear shape and provided directlyabove the vertical Hall element 100 with an intermediation of theinsulating film 30 in such a manner that a longitudinal center line ofthe excitation conductor 200 and a longitudinal center line of thesemiconductor layer (magnetism sensing part) 101 of the vertical Hallelement 100 coincide. The distance between the excitation conductor 200and the vertical Hall element 100 thereby becomes the smallest, andhence the intensity of the calibration magnetic field received by thevertical Hall element 100 can be made larger. Further, the uniformcalibration magnetic field can be supplied to the whole vertical Hallelement 100.

Then, in the present embodiment, the ratio W_(C)/W_(H) between the widthW_(C) of the excitation conductor 200 on the vertical Hall element 100and the width W_(H) of each of the electrodes 111 through 115 of thevertical Hall element 100 satisfies an inequality 0.3≤W_(C)/W_(H)≤1.0. Adescription will be made below as to the reason why such an inequalityis taken.

As the calibration magnetic field applied to the vertical Hall element100 and generated from the excitation conductor 200 becomes small, achange in the Hall voltage supplied from the vertical Hall element 100becomes small, thereby degrading the accuracy for estimation of actualsensitivity of the vertical Hall element 100. It is therefore preferableto apply the calibration magnetic field of 2 to 3 mT or more.

With the above in view, FIG. 2 illustrates a graph of a result in whichthe relation between the ratio W_(C)/W_(H) and an increase in thetemperature of the excitation conductor 200 when the excitationconductor 200 generates a magnetic field having a magnetic flux densityof 2 mT is simulated. Here, W_(C)/W_(H) is a ratio between the widthW_(C) of the excitation conductor 200 and the width W_(H) of each of theelectrodes 111 through 115 of the vertical Hall element 100 and thesimulation is made by changing a ratio h/W_(H) between a distance h fromthe center of the vertical Hall element 100, which is mainly constitutedfrom the semiconductor layer 101, in a substrate depthwise direction tothe excitation conductor 200 and the width W_(H) of each of theelectrodes 111 through 115 of the vertical Hall element 100.

It is understood from the graph of FIG. 2 that the increase in thetemperature of the excitation conductor 200 abruptly becomes large uponthe ratio W_(C)/W_(H) between the width W_(C) of the excitationconductor and the width W_(H) of each of the electrodes 111 through 115of the vertical Hall element reaching less than or equal to 0.3.Incidentally, FIG. 2 illustrates the simulation result in which theexcitation conductor 200 generates the magnetic field having themagnetic flux density of 2 mT as an example, it has been confirmed thateven when the excitation conductor 200 generates a magnetic field havinga magnetic flux density of 3 mT or more, the shape of the graph becomessimilar, and an increase in the temperature of the excitation conductor200 abruptly becomes large upon W_(C)/W_(H) reaching less than or equalto 0.3.

Accordingly, by setting the ratio W_(C)/W_(H) between the width W_(C) ofthe excitation conductor and the width W_(H) of each of the electrodes111 through 115 of the vertical Hall element to be greater than or equalto 0.3, it is possible to suppress the occurrence of a temperaturedistribution in the peripheral circuit upon applying a current to theexcitation conductor 200 to apply a calibration magnetic field of morethan 2 to 3 mT to the vertical Hall element 100.

On the other hand, the peripheral circuit and the excitation conductor200 approach each other when the width W_(C) of the excitation conductor200 becomes larger than the width W_(H) of each of the electrodes 111through 115 of the vertical Hall element 100. That is, the peripheralcircuit becomes vulnerable to the heat generation from the excitationconductor 200, and the accuracy of estimating the actual characteristicsof the vertical Hall element 100 is degraded. It is thus preferable thatin order to prevent the excitation conductor 200 from approaching theperipheral circuit, the width W_(C) of the excitation conductor 200 isnot made larger than the width of each of the electrodes 111 through 115of the vertical Hall element 100, i.e., the ratio W_(C)/W_(H) betweenthe width W_(C) of the excitation conductor and the width W_(H) of eachof the electrodes 111 through 115 of the vertical Hall element is set tobe less than or equal to 1.0.

FIG. 3 is a graph illustrating a result in which a relation between theratio W_(C)/W_(H) and a magnetic flux density (B/I) applied to thevertical Hall element 100 per unit current flowing through theexcitation conductor 200 is simulated. Here, W_(C)/W_(H) is a ratiobetween the width W_(C) of the excitation conductor 200 and the widthW_(H) of each of the electrodes 111 through 115 of the vertical Hallelement 100, and the simulation is made by changing the ratio h/ W_(H)between the distance h from the center of the vertical Hall element 100in a depthwise direction of the substrate to the excitation conductor200 and the width W_(H) of each of the electrodes 111 through 115 of thevertical Hall element 100.

It is understood from the graph of FIG. 3 that the magnetic flux density(B/I) applied to the vertical Hall element 100 per unit current flowingthrough the excitation conductor 200 becomes small as the ratio h/W_(H)between the distance h from the center of the vertical Hall element 100in the depthwise direction of the substrate to the excitation conductor200 and the width W_(H) of each of the electrodes 111 through 115 of thevertical Hall element 100 is made large. Hence the ration h/W_(H) ispreferably as small as possible.

Further, as can be seen from FIG. 2, the increase in the temperature ofthe excitation conductor 200 becomes large as the ratio h/W_(H) betweenthe distance h from the center of the vertical Hall element 100 in thesubstrate depthwise direction to the excitation conductor and the widthW_(H) of each of the electrodes 111 through 115 of the vertical Hallelement 100 is made lamer.

That is, as the distance h from the center of the vertical Hall element100 in the substrate depthwise direction to the excitation conductor 200becomes large, more current must flow to the excitation conductor 200 inorder to apply a required calibration magnetic field to the verticalHall element 100. The increase in the temperature of the excitationconductor 200 therefore becomes large, thereby affecting the peripheralcircuit.

Accordingly, even if the ratio W_(C)/W_(H) between the width W_(C) ofthe excitation conductor 200 and the width W_(H) of each of theelectrodes 111 through 115 of the vertical Hall element 100 is within arange which satisfies 0.3≤W_(C)/W_(H)≤1.0, the increase in thetemperature of the excitation conductor 200 is preferably 5° C. or lessto suppress affection to the peripheral circuit.

From FIG. 3, consequently, the ratio h/W_(H) between the distance h fromthe center of the vertical Hall element 100 in the substrate depthwisedirection to the excitation conductor 200 and the width W_(H) of each ofthe electrodes 111 through 115 of the vertical Hall element 100 ispreferably set to 0.4 or less at which the increase in the temperatureof the excitation conductor 200 becomes 5° C. or less in the range inwhich the ratio W_(C)/W_(H) between the width W_(C) of the excitationconductor and the width W_(H) of each of the electrodes 111 through 115of the vertical Hall element is 0.3 or more.

Incidentally, in a process of forming the vertical Hall element 100,forming the insulating film 30 thereon, and then forming wirings toelectrically connect the plurality of elements such as the transistorsconstituting the peripheral circuit to each other, the excitationconductor 200 can be formed simultaneously with the wirings. Accordingto the present embodiment, it is therefore possible to form theexcitation conductor 200 without increasing a manufacturing process.

Further, even if, for example, when W_(C)/W_(H) is designed to be 0.5,variation occurs in the width of the excitation conductor 200 due tovariations in the manufacturing process so that W_(C)/W_(H) becomes0.5+α or 0.5−α, a change in the magnetic flux density relative to itschange is small as can be seen from FIG. 3 because the ratio W_(C)/W_(H)between the width W_(C) of the excitation conductor 200 and the widthW_(H) of each of the electrodes 111 through 115 of the vertical Hallelement 100 is 0.3≤W_(C)/W_(H)≤1.0. That is, even if the width of theexcitation conductor 200 or the like varies due to the variations in themanufacturing process, a fluctuation in the intensity of the magneticfield generated from the excitation conductor 200 can be suppressed tobe small.

Here, resistivity of the excitation conductor 200 is preferably as lowas possible to reduce the amount of heat generation, e.g., theexcitation conductor 200 is preferably formed of Al or the like.Further, the excitation conductor 200 is preferably as thick as possibleto reduce the amount of heat generation, e.g., desirably 0.5 μm or more.

A description will next be made as to a method of compensating thecharacteristics of the vertical Hall element 100 in the semiconductordevice according to the present embodiment by the calibration magneticfield.

A current flow through the excitation conductor 200 generates acalibration magnetic field Bc having a predetermined magnetic fluxdensity indicated by a dotted line around the excitation conductor 200as illustrated in FIG. 1B, whereby the calibration magnetic field Bc isapplied to the vertical Hall element 100 in a horizontal direction. Atthis time, the predetermined magnetic flux density is preferably set tobe a few mT or so.

In a state in which the calibration magnetic field Bc is applied, adrive current is supplied to the electrode serving as a drive currentsupply electrode, of the electrodes 111 through 115 of the vertical Hallelement 100. Since the drive current receives the Lorentz force causedby the calibration magnetic field Bc, a potential difference isgenerated between the electrodes serving as Hall voltage outputelectrodes, of the electrodes 111 through 115 of the vertical Hallelement 100, whereby this potential difference is obtained as a Hallvoltage. Specifically, a Hall voltage is provided between the electrodes112 and 114 by, for example, supplying the drive current to theelectrodes 111, 113, and 115 in such a manner that a current flows fromthe electrode 113 to the electrodes 111 and 115.

The drive current and the gain of an amplifier connected to the outputof the vertical Hall element 100, etc. are adjusted based on the Hallvoltage obtained in this manner, an offset voltage remaining aftercalculation of a plurality of Hall voltages obtained by changing thedirection of supplying the drive current by a spinning current method,etc., thereby carrying out compensation of the characteristics of thevertical Hall element 100. It is thus possible to achieve asemiconductor device having the vertical Hall element 100 whichsuppresses variation in its characteristics with high accuracy.

The embodiment of the present invention has been described above, butthe present invention is not limited to the above embodiment. It isneedless to say that various changes can be made thereto within thescope not departing from the gist of the present invention.

For example, in the above embodiment, the excitation conductor 200 isillustrated in the single layer, but the thickness of the excitationconductor 200 may be increased as a whole by using a multilayer wiringto increase the whole thickness of the excitation conductor 200.

Also, there has been illustrated the example using AL or the like as theexcitation conductor 200, but a conductor such as polysilicon or thelike may be used.

Further, the first conductivity type and the second conductivity typehave been described as the P type and the N type respectively, but theymay be replaced with each other so that the first conductivity typefunctions as the N type and the second conductivity type functions asthe P type.

Furthermore, the above embodiment has illustrated the example in whichthe vertical Hall element 100 has the five electrodes, but the verticalHall element 100 may have three in total including two for the supply ofthe drive current and one for the output of the Hall voltage, or more.

What is claimed is:
 1. A semiconductor device, comprising: asemiconductor substrate of a first conductivity type; a vertical Hallelement provided on the semiconductor substrate; and an excitationconductor provided directly above the vertical Hall element with anintermediation of an insulating film, the vertical Hall elementcomprising: a semiconductor layer of a second conductivity type providedon the semiconductor substrate; and a plurality of electrodes eachconstituted from a high-concentration second conductivity type impurityregion, and provided on the surface of the semiconductor layer along astraight line, and a ratio W_(C)/W_(H) between a width W_(C) of theexcitation conductor and a width W_(H) of each of the plurality ofelectrodes satisfying an inequality 0.3≤W_(C)/W_(H)≤1.0.
 2. Thesemiconductor device according to claim 1, wherein the excitationconductor has a linear shape, and a longitudinal center line of theexciting conductor and a longitudinal center line of the semiconductorlayer of the vertical Hall element coincide.
 3. The semiconductor deviceaccording to claim 1, wherein a ratio h/W_(H) between a distance h fromthe center of the vertical Hall element in a substrate depthwisedirection to the excitation conductor and the width W_(H) of each of theplurality of electrodes is equal to or less than 0.4.
 4. Thesemiconductor device according to claim 2, wherein a ratio h/W_(H)between a distance h from the center of the vertical Hall element in asubstrate depthwise direction to the excitation conductor and the widthW_(H) of each of the plurality of electrodes is equal to or less than0.4.